Clinical observations have strongly implicated a number of antiseizure agents as human teratogens. The embryopathic potential of three classes of anticonvulsants: oxazolidinediones, hydantoins, and succinimides have been evaluated using the CD-1 mouse as the animal model. Estimated adult lethality curves were used as the basis for selecting doses for teratogenic investigations. Several dose levels with no observable maternal toxicity were evaluated. Following intraperitoneal administration, all the drugs were embryotoxic and produced not only intrauterine growth retardation, but also a range of malformations. Treatment on days 8-10 of pregnancy resulted in an increased incidence of congenital abnormalities in the skeletal and cardiovascular systems of the offspring while treatment on day 11-13 of pregnancy produced primarily cleft palate. In addition to their common teratogenic action, these compounds share a common chemical nucleus, namely a five membered imide ring. The finding that the three representative compounds are embryopathic strongly suggests a structure-teratogenic activity relationship. Upon comparing the relative teratogenicity of each anticonvulsant with respect to their relative risk to the dam, it was found that the teratogenicity of oxazolidinediones was significantly greater than that of the hydantoins and succinimides.